1. Field of the Invention
The present invention relates to recorded analog signals, and particularly relates to recorded analog signals spatially distributed in a modulated groove.
2. Related Art
Cavaglieri, S., Johnsen, O., and Bapst, F., in the Proceedings of AES 20th International Conference, Budapest, Hungary 2001, Oct. 5-7, presented a method of audio reconstruction wherein full size photographic contact prints are made of disc record surfaces. These films then serve as an archival medium, which are then scanned with a digital camera to retrieve the audio data. This retrieval method includes the extra step of traditional silver chemistry film photography, which may also add noise and degrade resolution. This method is a de facto two-dimensional approach due to the data originating from a single two-dimensional film image, with no three-dimensional analog. This archival method is only suited to lateral groove disc media and cannot accommodate cylinders or other vertically modulated media. Furthermore, this system maps the three-dimensional features of recorded grooves to a two-dimensional medium, thereby discarding the full three-dimensional information available in the original groove.
Stanke, G. and Paul, L., “3D Measurement and modeling in cultural applications”, Inform. Serv. & Use 15 (1995) 289-301, propose using a two-dimensional digital image capture as a method to measure the vertical groove modulation on the interior surfaces of cylinder molds (“Galvanos”). Stanke and Paul propose to use grey-scale intensity variations of the image as a quasi-measurement of height. This approach has only poor resolution due to the weak proportional relationship between actual surface height and grey-scale response.
Springer hosts a web site http://www.cs.huji.ac.il/˜springer/, which presents results from scanning of the surface of a disc recording by using a commercial desk-top scanner which thereby captures a digital image of the medium. Using this digital image the author attempts to reconstruct the audio data. However, the desk-top scanners have insufficient resolution to capture the subtle deflections of groove modulation in the media, and are also limited by a faulty assumed proportionality of grey-scale versus surface feature height. The direct scanning method is de facto two-dimensional, and thus also has no true three-dimensional analog. It cannot accommodate three dimensional media such as cylinder.